1. Field of the Invention
The present invention relates to a fly back transformer, and more particularly, to an improved fly back transformer capable of integrating a bleeder resistor to a high-voltage bobbin to downsize an article, reducing manufacturing cost, and readily drawing a focusing voltage during a process of winding high-voltage wires around a high-voltage bobbin so as to promptly conform with various article conditions.
2. Description of the Related Art
As well known in the art, a Fly Back Transformer (hereinafter will be referred to as FBT) is an apparatus mounted within a Braun Tube or Cathode Ray Tube (CRT) in a TV set or monitor for multiplying a pulse voltage from a horizontal output circuit for tens of times to generate a DC high voltage.
FIG. 1 shows a high-voltage stabilizing circuit in use for a general FBT. The high-voltage stabilizing circuit comprises a horizontal output circuit P receiving a horizontal synchronous pulse and generating a sawtooth wave, the first coil L1 with one end connected to an output terminal of the circuit P and the other end connected to a power source B+, the second coil L2 connected with a plurality of high-voltage rectifier diodes D1 to D5 for generating a high voltage HV, a bleeder resistor B/R stabilizing the high voltage HV from a high-voltage terminal of the second coil L2, a focusing circuit F outputting a plurality of focusing voltages and the third low-voltage circuit L3.
FIG. 2 is an exploded perspective view of a typical FBT. As shown in FIG. 2, a low-voltage bobbin 110a has a low-voltage wire wound around the same for plural times to constitute the first coil. A high-voltage bobbin 110 has an inner central opening into which the low-voltage bobbin 110a is inserted in a superposing manner. A plurality of high-voltage wires 113 are wound around the high-voltage bobbin 110 to constitute the second coil and a plurality of high-voltage rectifier diodes (hereinafter will be referred to as diodes) are connected to the high-voltage bobbin 110 in series. A focusing section 130 has a focusing pack 131 internally receiving a bleeder resistor 132. The focusing section 130 is mounted to one side of an FBT housing internally receiving the low- and high-voltage bobbins 110a and 110 and has a plurality of knobs for adjusting focusing voltages of a CRT. An anode cap supplies high voltage generated from a high-voltage terminal of the high-voltage bobbin 110 to the CRT through an anode cable 139.
The number of high-voltage wires 113 are wound around the high-voltage bobbin 110 of the above configured FBT 100 as follows: As shown in FIGS. 2 and 3, the first one of insulating films 114 is wound around the outer circumference of a hollow cylindrical bobbin body 111 and the first one of the high-voltage wires 113 is wound with a coil winder (not shown) around the first insulating film 114. The second one of the insulating films 114 is wound around the first wound high-voltage wire 113 and the second one of the high-voltage wires 113 is wound around the second insulating film 114. The above procedures are repeated in a radial outwardly to form a plurality of high-voltage coil layers, in which the outermost one of the insulating films 114 is wound around the outside surface of the outermost high-voltage coil layer so as to insulate the outermost high-voltage coil layer. Upon applying electric power, this configuration allows the potential difference among the wound coil layers to generate a high voltage, which is transferred through the anode cable 139 to the CRT.
In the high-voltage coil layers laminated in multiple interposing the insulating films 114 around the high-voltage bobbin 110, both ends of the high-voltage wires 113 each are alternately connected between an upper terminal pin 117 in any one of upper pin supporting portions 115 and a lower terminal pin 118 in any corresponding one of lower pin supporting portions 116. The upper pin supporting portions 115 are provided in plurality in an upper portion of the bobbin body 111, and the lower pin supporting portions 116 are provided in plurality in a lower portion of the bobbin body 111. Lead wires extended from both ends of the diodes 119 are electrically connected in series with one another.
Further, the focusing pack 131 of the focusing section 130 is internally mounted with a Printed Circuit Board (PCB) where an adjustable resistor portion is printed for adjusting the plurality of focusing voltages. The bleeder resistor 132 is electrically connected with the high-voltage terminal of the high-voltage bobbin 110 to drop the high voltage therefrom to a certain level of about 18 or 32% of the initial level, and fixedly mounted to one side of the focusing pack 131 with a holder 133.
The first pin terminal 137a and the second pin terminal 137b are fixedly installed in the focusing pack 131. The first pin terminal 137a is electrically connected with the first long pin 117a by inserting the first long pin 117a into the first pin terminal 137a, in which the first long pin 117a is an upper terminal pin of the high-voltage terminal outputting the high voltage. The second pin terminal 137b is electrically connected with the second long pin 117b by inserting the second long pin 117b into the second pin terminal 137b, in which the second long pin is another upper terminal pin disposed between the high-voltage terminal and a low-voltage terminal for drawing out the focusing voltage. The first and second pin terminals 137a and 137b are connected with the bleeder resistor 132 via cables 136a and 136b, and the high-voltage bobbin 110 is connected by its low-voltage terminal with an Automatic Brightness Limiter (ABL) circuit.
In such a conventional configuration as set forth above, however, since the focusing section 130 is necessarily provided with an additional space and holder for fixedly installing the bleeder resistor 132 in one side of the focusing pack 131, there are restrictions in downsizing the FBT 100 or reducing manufacturing cost.
Further, where the first long pin 117b corresponding to the first long pin 117a fixed in position is displaced in order to adjust the position of drawing the focusing voltage, it is needed to identically displace the second pin terminal 137b into which the second long pin 117b is correspondingly inserted. This creates a very complicated and troublesome assembly process while failing to promptly coping with various design requirements from consumers as drawbacks.
The present invention has been made to solve the conventional problems as set forth above and it is therefore an object of the present invention to provide an FBT capable of readily displacing the drawing position of focusing voltage during the operation of winding high-voltage wires around a high-voltage bobbin so as to promptly correspond to various article conditions.
It is another object of the invention to provide an FBT capable of connecting one end of a high-voltage terminal and a drawing terminal of focusing voltage to a bleeder resistor and integrating the bleeder resistor to a high-voltage bobbin. without using long pins and pin terminals so as to downsize final articles as well as reduce manufacturing cost.
According to an aspect of the invention to obtain the above objects, it is provided a fly back transformer for providing a DC high voltage and at least one focusing voltage to a CRT in a TV set or monitor, comprising: a horizontal output section for receiving horizontal synchronous pulse and generating sawtooth wave; a low-voltage bobbin having a low-voltage wire wound around the outside surface thereof to form a first coil; a high-voltage bobbin having a plurality of high-voltage wires wound for plural times interposing insulating films around the high-voltage bobbin to form a second coil having a number of high-voltage coil layers and a plurality of high-voltage rectifier diodes each connected in series between each of plural upper terminal pins and each of plural lower terminal pins; a focusing pack having a PCB internally mounted thereto by molding insulating resin, the PCB being printed with an adjustable resistor to adjust the at least one focusing voltage, and a focus input terminal for receiving the focusing voltage; a bleeder resistor detachably fixed in position to the high-voltage bobbin, and having an upper end electrically connected with one of the upper terminal pins corresponding to a high-voltage terminal to output the final high voltage generated from the high-voltage bobbin and a lower end electrically connected to the focus input terminal; and a focus-drawing wire disposed between the first one of the high-voltage coil layers and the last one of the high-voltage coil layers, and having one end connected with the upper terminal pin to draw a voltage generated between the high-voltage terminal and a low-voltage terminal of the high-voltage bobbin and the other end connected with the lower end of the bleeder resistor electrically connected with the focus input terminal of the focusing pack.
According to another aspect of the invention to obtain the above objects, fly back transformer for providing a DC high voltage and at least one focusing voltage to a CRT in a TV set or monitor, comprising: a horizontal output section for receiving horizontal synchronous pulse and generating sawtooth wave; a low-voltage bobbin having a low-voltage wire wound around the outside surface thereof- to form a first coil; a high-voltage bobbin having a plurality of high-voltage wires wound for plural times interposing insulating films around the high-voltage bobbin to form a second coil having a number of high-voltage coil layers and a plurality of high-voltage rectifier diodes each connected in series between each of plural upper terminal pins and each of plural lower terminal pins; a focusing pack having a PCB internally mounted there to by molding insulating resin, the PCB being printed with an adjustable resistor to adjust the at least one focusing voltage, and a focus input terminal for receiving the focusing voltage; a bleeder resistor detachably fixed in position to the high-voltage bobbin, and having an upper end inserted into an inserting member in an upper side of the bobbin body and a lower end inserted into a settling member in a lower side of the bobbin body, the upper end being electrically connected with one of the upper terminal pins corresponding to a high-voltage terminal and the lower end being electrically connected with the focus input terminal; and a focus-drawing wire disposed between the first one of the high-voltage coil layers and the last one of the high-voltage coil layers, and having one end connected with the upper terminal pin to draw a voltage generated between the high voltage terminal and a low-voltage terminal of the high-voltage bobbin and the other end connected with the lower end of the bleeder resistor.